Spark plug



F. A. BUCHAN Dec. 18, 1956 SPARK PLUG Filed Feb. 9. 1953 vrs- United States Patent` SPARK PLUG Frank A. Buchan, Cochrane, Ontario, Canada Application February 9, 1953, Serial No. 335,753

3 Claims. (Cl. 313-125) r[his invention has reference to spark plugs for internal combustion engines and pertaining particularly to new and useful improvements in plugs of the adjustable gap variety.

The invention contemplates the provision of a spark plug in which the spark gap may be quickly and easily set to the engine makers speciiications.

The invention contemplates further the provision of a spark plug in which the spark gap may be quickly and easily set to a required value without removing the plug from the engine block.

The invention further contemplates the provision of a spark plug in which the spark gap may be quickly and easily set to a required value by adjustment of the usual central high potential electrode.

The invention envisages further the provision of a spark plug in which the spark gap may be quickly and easily set to a required value, by adjustment of the usual central electrode, without removing the plug from the engine block.

Contemplated yet further by the invention is the provision of a calibrated spark plug in which a desired gap setting may be achieved by micrometer adjustment of the usual central electrode without removing the plug from the engine block.

These and other objects and advantages of the present invention will become more apparent as the following description proceeds, particularly when reference is had to the accompanying drawing wherein:

Figure l is an elevational view of one embodiment of the invention, and

Figure 2, is a sectional elevation of the embodiment of Figure 1.

It is customary, in order to adjust the gap of the usual spark plug to forcibly bend the low potential (ground) electrode towards or away from the xed position high potential (central) electrode until the required gap setting is obtained.

This method of adjustment is not entirely satisfactory; iirst, because it is necessary to remove the plug from the engine block; second, because the adjustment process necessitates the use of a thickness gauge, and third, because of the crudity of the method of adjustment.

The present invention contemplates the elimination of these disadvantages by providing a spark plug formed with an integral gap adjusting means.

Broadly the invention comprises a conventional spark plug having the central electrode adapted for adjustable movement towards or away from the ground (shell) electrode. A calibrated scale and locking means are provided for ease and permanence of gap adjustment.

One embodiment of the inventive idea is disclosed in the drawing, and, by reference to the gures thereof, it will be noted that the spark plug includes a hollow metal body member, designated by the reference character 10, which is adapted by an externally threaded portion 11 for insertion in the cylinder head of an engine. Formed integrally with the bottom most edge of the threaded portion 11 is an electrode 12 which, as shown, is formed radially inwardly in usual fashion towards the longitudinal axis of the body member 10.

Secured partially within the body member 10 is a longitudinal insulating member 13 of porcelain or other suitable material and which, as illustrated, may preferably be formed with a taper from its central portion towards each end and with an axial box 14. f

A longitudinally calibrated circular stud 15, of metal or other suitable material, having a circumferential bearing ange 16 and an internally threaded longitudinal axial bore 17, is rigidly secured to the outer and uppermost end of the insulating member 13 in any suitable fashion, e. g. by an externally threaded terminal portion 18 in engagement with a corresponding mating portion formed in the upper end of the member 13.

Extending axially through the insulating member 13 and stud 15 for vertical and revolvable movement is a central electrode 19 having the upper termination thereof externally threaded for engagement with the internally threaded bore 17 of the stud l5, and having its lower termination disposed adjacent the irst said electrode 12 so as to form a spark gap.

A metal cap 20 having a vertical threaded binding post 21 is attached to the upper 'threaded end of the electrode 19 and moves therewith vertically of the stud 15. The cap 20 is calibrated peripherally of its lower tapered edge, which calibration, in conjunction with the calibration of the stud 15, provides a direct indication of the gap between the electrodes 12 and 19. A screw 22 is threadably attached to the binding post 21 for the usual high potential electrical connection.

Encircling the stud 15 for revolvable movement, and secured thereto by a plurality of lingers 23 extending from the flange 16 of the said stud, is a locking ring 24 the inner diameter of which is formed with an eccentric portion for the actuation of a locking pin 25, which latter is slidably secured radially of the stud 15 for locking the electrode 19 in a set position.

It is obvious, of course, that the electrode 19 may be extended through the cap 20 for use as a binding post, and that the cap 20 and stud 13 may be formed in other fashion and of other materials without departing from the spirit of the invention. The form shown in the drawing is illustrative of one embodiment of a spark plug wherein the central electrode is adapted for calibrated movement towards lor away from the ground (shell) electrode of the plug.

In use, the gap is set to the required value by reference to the calibrated Iscale whereupon the ring 24 is rotated to lock the central electrode 19 in the adjusted position. While the zero of the calibrated scale may be invalidated by electrode wear it is apparent that a new zero may be readily established by closing the spark gap.

It is believed that the construction and advantages of the structure shown may be apparent from the foregoing paragraphs taken in conjunction with the accompanying drawings without further detailed description.

While the preferred embodiment of the invention has been disclosed it is understood that minor changes in the construction, combination and arrangement of co operating parts may be resorted to within the scope of what is claimed without departing from the spirit of the invention.

I claim:

1. An adjustable spark plug comprising, an approximately cylindrical shell formed with an externally threaded terminal portion, a terminal electrode formed in tegrally with the said terminal portion and extending radially inwardly past the center of the said shell, an insulator bored along its major axis and secured partially within the said shell, a longitudinally calibrated stud Ysecured-to `the outermost end of -the .said insulator,

the said stud having an axial internally threaded bore formed therein, a longitudinal electrode extending axially -through the said yinsulator and said stud for movement 4attached to the said post, a `locking pin slidably mounted in said stud at right angles to said longitudinal electrode, and a ring encircling the said stud and secured thereto for revolvable movement, the inner diameter of the said ringlbeing formed with an eccentric Aportion for engaging and moving said pininto `locking engagement with said longitudinal electrode.

2. A spark plug for `internal combustion engines, an

insulator, van internally threaded axially bored longitudinally calibrated stud axially lterminally secured .to the -said insulator, acentral electrode having one end thereof externally threaded, extending through the said insulator and said stud and movable towards or away from a Xed second electrode, a peripherally calibrated metal cap terminally secured to the said central electrode, a pin Lslidably mounted radially in the said stud for locking engagement with said central electrode, and a ring encircling the said -stud and pin and secured thereto for revolvable movement, the inner surface of the said ring being formed with an eccentric portion for the actuation of the said pin.

3. An adjustable spark plug comprising a shell having a fixed electrode, an insulator core xed within said shell having a central longitudinal bore, a stud extending from the upper end of said core having a bore in alinement with the bore of said core and provided with internal screw threads, a central electrode extending through the bore of said core and stud having external screw threads for engagement with the threaded bore of said stud,.a cap iixedly secured to the upper end of said central electrode forturning the electrode to move the electrode longitudinally of the bore of said core, a locking pin slidably mounted in said stud radially of the central electrode with its inner end in engagement with the electrode, and a ring rotatably mounted on said stud having a cam surface on its inner periphery adapted to engage the outer end of said locking pin to force said pin into locking engagement with said central electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,401,585 Collins et a1. Dec. 27, 1921 FOREIGN PATENTS 112,720 Great Britain Ian. 24, 1918 

